The present invention pertains to an improved drill bit for forming boreholes as in drilling oil and gas wells. Moore particularly, the present invention pertains to drill bits which employ and contain polycrystalline diamond cutting elements, and are usually referred to as "PDC" drill bits.
Many "PDC" drill bits of the prior art experience a destructive whipping action, or radial vibration of the drill bit which randomly occurs during rotary operation due to clearance between the outside of the drill bit and the wall of the borehole. This whipping tendency intensifies in proportion to the hardness or toughness of the formation being drilled and in proportion to the rotational speed of the drill bit, causing impact contact between the cutting elements of the drill bit and the formation material being drilled, which in turn results in fractured, chipped, or displaced cutting elements, thus drastically shortening the operating life of the drill bit and causing the operating life to be inconsistent and unpredictable.
Another problem often found in prior art "PDC" drill bits is erosion which is caused by high velocity drilling fluid acting on the cutting mountings of the cutting elements, on the drill bit face, and on other components of the bit. This shortens the operating life of the drill bit.
Another problem associated with prior art "PDC" drill bits is balling, plugging, or packing of cut material onto the face of the drill bit due to uneven or unbalanced fluid flow over the face of the drill bit which results in reduced penetration rates and inadequate and uneven cooling of the cutting elements and thereby unpredictably diminish the resultant drilling operation.
Because of the above problems, "PDC" drill bits have heretofore been used economically only in drilling a very limited range of different rock and earth formations. U.S. Pat. Nos. 712,887 (Wyczynski); 2,857,141 (Carpenter); and 3,062,303 (Schultz) each contain radially acting stabilizing means. However, as the respective specifications show, each of those are based on considerably different and less effective principles of operation than the present invention.